1. Field of The Invention
This invention relates to a switchgear used for opening or closing the line by interposing it in the high or extra-high voltage transmission line or power distribution system, and more particularly to a switchgear used for opening the circuit while the current flows through said line or for connecting the loads to the line and more specifically to a method for extinguishing the arc which generates during the switching action between a pair of fixed and movable electrodes within the switch.
2. Description of The Prior Art
A construction as shown in FIG. 6 is known as an art of this sort. In case, in such a construction, a movable electrode 42 is connected to a fixed electrode 41, in the high voltage switchgear 40, an alternating current flows from the high voltage power supply 43, e.g. high voltage line which leads to the substation through the above-mentioned electrodes 41 and 42 to the load 44 e.g. high voltage distributing line which leads to consumers. In this case, when the current is cut off, a movable electrode is drawn out from the fixed electrode in the direction of the arrow. In this process, when the movable electrode 42 is separated from the fixed electrode 41, if a polarity of the power supply voltage is directed in the forward direction relative to a diode 46, a current which directs from the fixed electrode 41 toward the movable electrode 42 is shifted from the fixed electrode 41 through a resistance 47, diode 46 and an auxiliary electrode 45 to a bypass directing toward the movable electrode 42.
Subsequently, when said supply voltage obtained an inversed polarity, the current which passes said bypass is cut off. Since at this stage the movable electrode 42 is separated from the auxiliary electrode 45, the arc is not generated between those electrodes 42 and 45. Of course, the current does not flow between said electrodes 42 and 41. The above-mentioned art is known, e.g. in Japanese Patent Laid-Open No. 39-25702 (page 1, right column line 6 to 19).
However, the circuit of above switchgear 40 is not always opened when the supply voltage displayed the polarity as described but following cases can occur: when the movable electrode 42 is separated from the fixed electrode 41, a polarity of the supply voltage can display an inversed direction relative to the diode 46, in which case since the diode 46 is cut off, an arc is generated between electrodes 41 and 42. The arc continues while the above-mentioned polarity is inverted, e.g. for a half cycle of the alternating current. Thus both electrodes suffer from a great damage due to the application of heat caused by the arc which continues over a long time.
Furthermore, while the arc is generated as mentioned above, the movable electriode 42 is separated from the fixed electrode 41. Consequently, the arc generated between both electrodes 41 and 42 is increased until the atmosphere between both electrodes is ionized. The atmosphere thus ionized encourages a reignition between elctrodes 41 and 42 when subsequent to the supply voltage having attained a value of 0 v. a polarity is inversed. Thus the arc is again generated between both electrodes, further intensifying the damage of both electrodes.